Transmission line



Feb. 23, 1960 D. BLITZ TRANSMISSION LINE Filed March 11, 1954 n. 3 w/ w..W. F m M ha v. i m m z 9 m .m 7 S F N/a I! w Daniel Blitz IN V EN TOR.

United States Patent TRANSMISSION LINE Daniel Blitz, Boston, Mass.,assignor, by mesne assignments, to Sanders Associates, Incorporated,Nashua, N.H., a corporation of Delaware Application March 11, 1954,Serial No. 415,493

Claims. (Cl. 333-84) The present invention relates to transmissionlines. More particularly, the present invention relates to the use oftransmission lines such as are used in association with high frequencyelectronic devices.

In modern shortwave techniques, transmission lines in a form familiarlyknown as wave guides are widely used. Because of the construction thesewave guides occupy a large volume of space, are heavy and are expensiveto manufacture.

Theoretically, a transmission line composed of inner conductors offinite width and spaced between outer conductors that are parallel andof infinite width would permit no radiation of high frequency energyfrom the line. By selecting the width of the outer conductors to besufiicient- 1y greater than that of the inner conductors, a transmissionline of relatively low loss due to radiationis obtained.

Asan alternative to wave guides, these configurations may be morereadily employed with printed and etched circuit techniques. Apropensity of these alternative con figurations toward the propagationof high frequency energy in undesirable modes has been the source ofmuch difficulty.

It is therefore an object of the present invention to provide animproved transmission line that excludes undesirable propagation modesof high frequency energy; and

A further object of the invention is to provide an improved transmissionline of the character described in which the relative movement of itsparts has substantially no effect on the electrical characteristics ofthe line.

Other and further objects of the invention will be apparent from thefollowing description of a typical embodiment thereof, taken inconnection with the accompanying drawings.

In accordance with the invention there is provided a composite,high-frequency, electric transmission line. The line includes a pair ofthin, elongated, parallel, planar, etched-circuit-type, outer conductorsproviding electrical ground planes. A thin, elongated planar,etched-circuittype inner conductor is disposed in parallel with andbetween the outer conductors. The inner conductor is of lesser widththan the outer conductors. A solid dielectric, planar insulating panelwider than the inner conductor is disposed between the inner conductorand one of the outer conductors for securing the inner conductor ininsulated spaced relation with respect to the outer conductor. Anothersolid dielectric planar insulating panel is secured to the other of theouter conductors and is disposed between the inner and the otherouterconductor. A pair of thin, elongated, planar, etched-circuit-type,capacitive, strip conductors are affixed to a surface of the firstinsulated panel adjacent opposite sides of the inner condoctor. Thecapacitive strip conductors are spaced transversely less than a halfwave length apart at the highest operating frequency. A second pair ofthin, elongated, etched-circuit-type capacitive stripconductors areaffixed to the second insulating panel. They are so disposed as toregister with the first pair of strip conductors. The

facture and reliability of operation of these be wider than conductor 14thickness of the strip conductors is so chosen relative to the innerconductor as to provide a space between adjacent ones of the stripconductors in register. Conductive rods extend from the outer conductorsthrough the insulating panel through the adjacent strip conductorscorresponding with each outer conductor to effect an electrical couplingbetween the outer conductors. This enables relative movementtherebetween without substantially varying the electricalcharacteristics of the transmission line.

In the accompanying drawings:

Fig. 1 is a three-dimensional view of a three-plate transmission lineembodying this invention;

Fig. 2 is a cross-sectional view of a four-plate transmission lineembodying the present invention;

Fig. 3 is a cross-sectional view of a four-plate transmission lineillustrating another embodiment of the invention;

Fig. 4 is a schematic diagram of a source of energy connected to thetransmission line of Fig. l; and

Fig. 5 is a schematic diagram of a source of energy connected to thetransmission line of Fig. 2.

Referring now in more detail to the drawings, an outer.

conductor 1 is attached to the upper surface of a dielectric 2 with asuitable cement. An inner conductor 3 is attached to the under surfaceof the dielectric 2. An outer conductor 5 is attached to the undersurface of a dielectric 4. Pins 7 pierce outer conductor 1, dielectric 2and contact strip 6. Pins 7 pierce outer conductor 5 and dielectric 4.Outer couductors land 5 are capacitively coupled through. contact strip6 and pins 7 because of their proximity. The pins 7 are positioned inpairs in the direction of the length of the line at intervals 8 lessthan a quarter-wave long at the operating frequency and at transverseintervals 10 less than a half-wave long at the operating frequency. Thisarrangement permits limited relative transverse movement between theline sections as shown, without substantially varying the electricalcharacteristics of the line.

In Fig. 2 there is shown an embodiment of this invention wherein afour-plate line is provided. The inner conductors 13 are connected tothe same voltage source. Since the fields between each inner conductorand its associated outer conductor are maintained relatively constant,limited transverse motion between the inner conductors in the directionas indicated at 9 is permissible without substantially varying theelectrical characteristics of the line. As shown in Fig. 3, innerconductor 15 may to permit limited transverse motion between them in thedirection as indicated at 17.

In Fig. 4 a source 16 of high frequency energy is shown connected to thethree-plate transmission line of Fig. 1, viewed in longitudinalcrosssection. The inner conductor 3 is connected to one electrical side;the outer conductors 1 and 5 are connected together to the ground sideof source 16.

In Fig. 5 the source 16 is shown connected to the fourplate transmissionline of Fig. 2, viewed in longitudinal cross-section. The innerconductors 13 are connected together to one side of the source; theouter conductors are connected together to the ground side 15, as shown.

Since the physical parameters of the transmission line as describedabove may be varied without substantially reducing the efficiency of theline, the economy of manudevices is greatly enhanced.

While there has been hereinbefore described what is at presentconsidered a preferred embodiment of the invention, it will be apparentthat many and various changes and modifications may be made with respectto the embodiment illustrated without departing from the spirit of theinvention. It will be understood, therefore, that all those changes andmodifications as fall fairly within the scope of the present invention,as defined in the appended claims, are to be considered as a part of thepresent invention.

What is claimed is: V

l. A composite, high-frequency, electric, transmission line, comprising:a pair of thin, elongated, parallel, planar, etched-circuit-type, outerconductors providing electrical ground planes; a thin, elongated,planar, etched-circuit-type, inner conductor disposed in parallel withand between said outer conductors, said inner conductor being of lesserwidth than said outer conductors; a first solid, dielectric, planar,insulating panel wider than said inner conductor and disposed betweensaid inner conductor and one of said outer conductors for securing saidinner conductor in insulated, spaced relation with respect to said outerconductor; a second solid, dielectric, planar, insulating panel securedto the other of said outer conductors and disposed between said innerand said other outer conductor; a pair of thin, elongated, planar,etched-circuit-type, capacitive, strip conductors aflixed to a surfaceof said first insulating panel adjacent a side of said inner conductorand spaced tranversely less than a half wave length apart at theoperating frequency; a second pair of thin, elongated,etched-circuit-type, capacitive strip conductors affixed to said secondinsulating panel and so disposed as to register with the first said pairof strip conductors, the thickness of said strip conductors being sochosen relative to saidinner conductor as to provide a space betweenadjacent ones of said strip conductors in register; and conductive rodsextending from Said outer conductors through said insulating panel tosaid adjacent strip conductors corresponding with each outer conductorto eifect an electrical coupling between said outer conductors and toenable relative movement therebetween without substantially varying theelectrical characteristics of said transmission line.

2. A composite, high-frequency, electric, transmission line, comprising:a pair of thin, elongated, parallel, planar, etched-circuit-type, outerconductors providing electrical ground planes; a thin, elongated,planar, etchedcircuit-type inner conductor disposed in parallel with andbetween said outer conductors, said inner conductor being of lesserwidth than said outer conductors; a first solid, dielectric, planar,insulating panel wider than said inner conductor and disposed betweensaid inner conductor and one of said outer conductors for securing saidinner conductor in insulated, spaced relation with respect to said outerconductor; a second solid, dielectric, planar, insulating panel securedto the other of said outer conductors and disposed between said innerand said other outer conductor; a pair of thin elongated, planar,etchedcircuit-type, capacitive, strip conductors affixed to a surface ofsaid first insulating panel laterally adjacent opposite sides of saidinner conductor and spaced transversely less than one-half wave lengthapart at the highest operating frequency; a second pair of thin,elongated, etchedcircuit-type capacitive strip conductors affixed tosaid second insulating panel and so disposed as to register with thefirst said pair of strip conductors, thethickness of said stripconductors being so chosen relative to said inner conductor as toprovide a space between adjacent ones of said strip conductors inregister; and means for supporting and electrically coupling said stripconductors to said outer conductors to enable relative movement of saidouter conductors without substantially varying the electricalcharacteristics of said transmission line.

3. A composite, high-frequency, electric, transmission line, comprising:a pair of thin, elongated, parallel, planar, etched-circuit-type, outerconductors providing electrical ground planes; a pair of soliddielectric, planar, insulating panels secured to said outer conductorsand disposed between said outer conductors; a pair of thin, elongated,planar, etched-circuit-type, inner conductors disposed in register andin parallel with and between 4 said outer conductors, said innerconductors being of lesser width than said outer conductors and bondedto the inner surfaces of said solid, insulating panels; pairs of thin,elongated, planar, etched-circuit-type, capacitive, strip conductorsafiixed to the inner surface of each insulating panel laterally adjacentopposite sides of each inner conductor and spaced transversely less thanonehalf a wave length apart attthe highest operating frequency, thethickness of said strip conductors being so chosen relative to saidinner conductors as to provide a space between adjacent ones of saidstrip conductors in register; and means for supporting said stripconductors to effect an electrical coupling between said outerconductors and to enable relative movement therebetween withoutsubstantially varying the electrical characteristics of saidtransmission line.

4. A composite, high-frequency, electric transmission line, comprising:a pair of thin, elongated, parallel, planar, etched-circuit-type, outerconductors providing electrical ground planes; a pair of solid,dielectric, planar, insulating panels secured to said outer conductorsand disposed between said outer conductors; a pair of thin, elongated,planar, etched-circuit-type, inner conductors of differing widthsdisposed in register and in parallel with and between said outerconductors, said inner conductors being of lesser width than said outerconductors and bonded to the inner surfaces of said solid insulatingpanels; pairs of thin elongated, planar, etched-circuittype, capacitive,strip conductors atfixed to a surface of each insulating panel laterallyadjacent opposite sides of each of said inner conductors and spacedtransversely less than one-half wave length apart at the highestoperating frequency, the thickness of said strip conductors being sochosen relative to said inner conductors as to provide a space betweenadjacent ones of said strip conductors in register; and means forsupporting said adjacent strip conductors to effect an electricalcoupling between said outer conductors and to enable relative movementtherebetween without substantially varying the electricalcharacteristics of said transmission line.

5. A composite, high-frequency, electric, transmission line, comprising:a pair of thin, elongated, parallel, planar, etched-circuit-type, outerconductors providing electrical ground planes; a pair of solid,dielectric, planar, insulating panels secured to each of said outerconductors and disposed between said outer conductors; pairs of thin,elongated, planar, etched-circuit-type, inner conductors of differingwidths disposed in register and in parallel with and between. said outerconductors, said inner conductors being of lesser width than said outerconductors and bonded to the inner surfaces of said insulating panels;pairs of thin, elongated, planar, etched-circuit-type capacitive stripconductors afiixed to the surfaces of each of said insulating panelslaterally adjacent opposite sides of said inner conductors and spacedtransversely less than one-half wave length apart at the highestoperating frequency, said strip conductors being in register and of athickness chosen relative to said inner conductors as to provide a spacebetween adjacent ones of said strip conductors in register; andconductive rods extending from said outer conductors throughsaid'insulating panels to said adjacent strip conductors correspondingwith each outer conductor to effect an electrical coupling between saidouter conductors and to enable relative movement therebetween withoutsubstantially varying the electrical characteristics of saidtransmission line.

References Cited in the file of this patent UNITED STATES PATENTS2,155,508 Schelkunoff Apr. 25, 1939 2,445,380 Zottu July 20, 19482,603,749 Kock July 15, 1952 (Other references on following page) V E")6 UNITED STATES PATENTS 570,087 Great Britain June 21, 1945 Grieg Oct18, 1955 1 601,514 Great Britain May 7, 1948 Blitz Oct. 20, 1957 SommersNov. 5, 1957 OTHER REFERENCES v 5 Radio, Electronic Engineering";September 1951; pp. FOREIGN PATENTS 16 and 31. 7

Great Britain Nov. 25, 1941

